The present invention relates to the field of display devices, such as signs, nameplates and tags, and, more particularly, to a display device used in harsh environments where durability is at a premium.
There are many applications in which a display device is exposed to harsh environments. For example, it is often necessary to identify cables which are buried beneath the ground for extended periods, or to label outdoor utility poles with identifying information.
The particular application doesn't matter. The commonality of such applications is that the display device used to identify the cable, or label the pole, etc., must be capable of withstanding extremes of temperature, humidity (from arid desert to periodic flooding), abrasion, ultraviolet exposure or acidity, among other hazards, without undue degradation or cost.
Most consumers of such display devices, prefer to use generally identical devices for any environment, rather than purchase special display devices for each environment. This minimizes costs by permitting the purchaser to buy in quantity, and by permitting him also to reduce his inventory.
It is also preferred that the devices be as inexpensive as possible.
Thus, there is a need for a display device which is durable in any of a plurality of harsh environments, and which is also inexpensive to manufacture.
Currently, there are many display devices which attempt to fill this need. For example, there exist flat, molded or embossed metal tags upon which indicia (e.g. letters, numbers or other identifying material) are painted in a color selected to contrast with that of the background thereof. While the metal of the tags may be of fairly high durability, the painted indicia tend to abrade, peel and otherwise deteriorate, thereby rendering the tag difficult to read. Such tags are also of relatively high cost and are electrically conductive, which is often undesirable for display devices.
Other commercially available display devices comprise unitary plastic tags which may have a flat surface, or have a raised or recessed surface configured in the shape of the desired indicia. The indicia are then painted on the background material, or otherwise colored, such as by hot stamping or silk-screening, with a coating of a desired contrasting color.
Such tags are inexpensive to manufacture, but not very durable. While the type of plastic conventionally used in the tags does not degrade easily, the indicia coloring is usually not of any great thickness (generally no more than a few thousandths of an inch), and easily abrades off, or fades after prolonged exposure to ultraviolet radiation. There is a particular problem with applying a coloring to the surface of the device, since it is difficult to achieve good adhesion between the coloring and the underlying plastic.
Furthermore, there is an existing problem with the proper application of the coloring to the surface of the raised indicia, since this involves two separate aligning steps, and the device may not be properly aligned during the second step.
There exists a particular problem in the so-called "hot-stamp" process, in which the coloring of the indicia is deposited on the background with a foil colorant. Even if the colorant appears to be satisfactorily applied, its adhesion to the background material is subject to wide variation. Additionally, quality control is difficult, since each piece must be actually tested, rather than merely inspected. Alternatively, it is possible to forego inspection, resulting in a less expensive, but less reliable, product.
While there also exist many thick plastic display devices, none of them are readily adaptable to the fields of use herein described.
It is preferred that display devices be as thin as possible, since this reduces the materials cost of the device, and it also permits the display device to be more readily bent, which is necessary in some applications, e.g. labeling curved poles or cables. Furthermore, thick display devices also project further from the surface of the object being labelled, so that they are more prone to be damaged by a lateral impact thereto.
It is also known to manufacture a display device as two separate pieces: a display portion and a background portion. Such known devices, however, must be assembled, which adds manufacturing costs, and must also utilize a third, retaining, portion, to hold the other two pieces together. Thus, such devices are less attractive from a practical standpoint.
There is thus a need for an inexpensive display device having high durability in a plurality of harsh environments, particularly with respect to ultraviolet, abrasive or harsh chemical environments.